1. Field of the Invention
The invention relates to a method of producing a curved rod and a rod produced by the method.
2. Description of the Related Art
Fiber reinforced rods have been used for stiffening flexible structures. These rods are produced by impregnating fibers, for example glass fibers, with resin, such as polyester resin. A lighter and more stable rod is obtained after curing, i.e. after the fibers have been crosslinked with the resin. Fiber reinforced rods usually are straight. Stresses occur if such a straight rod is employed in a structure in which the rod is held in a constantly curved state. Accordingly, the bearings for holding the rod in its curved position may suffer fatigue. There has been a proposal to grind the surface of the rod at certain locations to influence the form of a desired bend. This constriction prevents fatigue of the bearings, but requires great subsequent working effort and weakens the fibers of the rod.
U.S. Pat. No. 5,470,517 generically discloses a method of producing a curved rod in which the curing, i.e. the crosslinkage of the resin with the fibers, is performed while the rod is bent as desired. The fibers of the bent rod produced by the method are not weakened by subsequent constriction and the rod does not induce any effects of fatigue at its bearings.
A bent rod made by the method generically disclosed in U.S. Pat. No. 5,470,517 represents a usable solution for various application areas. However, the rod bent by the method disclosed generically in U.S. Pat. No. 5,470,517 continues to have disadvantages in certain cases. More particularly, continual relative movements may take place between the above-described rod and a structure stiffened by the rod. This movement creates problems of friction between the hard rod and the flexible material surrounding it, for example rubber. This situation may arise in the stiffening of a flexible air ducting device of a motor vehicle, which is intended to change its form according to the driving situation of the motor vehicle, and which is subjected to the continual movements of the motor vehicle. To achieve bent rods that are adapted to such harsh operating conditions, it has already been proposed to provide the rod with a nonstick coating or to wind a high-grade steel spiral around the rod. However, the nonstick coating peels off under the harsh operating conditions and the high-grade steel spiral represents a relatively complex solution. Hence, there is a need for improvements to bent fiber reinforce rods. Consequently, an object of the invention is to provide a rod that avoids the problems mentioned above.